She later told AFP that most had fled from the embattled eastern regions of Donetsk and Lugansk, where Ukrainian forces are battling separatists from the Russian-speaking community.

But she underlined that it was not possible to say whether most or all of those fleeing to neighbouring Russia were from Ukraine’s Russian-speaking population.

Claims that Russian-speakers in Ukraine are under threat have been cited regularly by the rebels and Moscow, though UN human rights probes have said there is little evidence for such fears.

Only a relatively small proportion of those fleeing to Russia have formally asked the country for a haven, Fleming said.

“Only 9,500 have requested asylum. Most people are seeking other forms of legal stay, often because they’re concerned about complications involving seeking asylum or since there might be reprisals if they return to Ukraine,” she said, without elaborating.

Most of the most recent arrivals are clustered in the western Russian cities of Rostov-on-Don and Bryansk, near the Ukrainian border, said Fleming.

Close to 13,000 people, including 5,000 children, are being accommodated mainly in public buildings and tented camps in Rostov-on-Don.

In Bryansk, where 6,500 arrived in recent days, the majority are staying with friends and relatives.

Within Ukraine itself, 16,400 people have fled their homes in the east in the past week alone, taking the total number of internally-displaced to 54,400.

– Reasons for fleeing –

“The rise in numbers of the past week coincides with a recent deterioration of the situation in eastern Ukraine. Displaced people cite worsening law and order, fear of abductions, human rights violations and the disruption of state services,” Fleming said.

Russian-speaking militants rose up after the February ouster of pro-Moscow president Viktor Yanukoyvch by a coalition of pro-Western groups and nationalists.

He was forced from power after months of protests following his last-minute decision not to sign a deal cementing the economically-embattled, ex-Soviet republic’s ties with the European Union.

Instead, he opted to turn to former master Moscow for economic backing, sparking uproar in the pro-Western camp.

Ukraine’s new leadership signed an agreement with the European Union on Friday.

Moscow in March annexed Ukraine’s strategic Crimea peninsula, mainly populated by Russian speakers and long home to Russian military bases.

At least 12,000 members of Crimea’s Muslim Tatar community have fled to other parts of Ukraine since the annexation, according to the UN.

Russia denies claims that it is stoking strife by sending in men and weapons to Russified eastern Ukraine, where government forces have been battling rebels for weeks.

Fleming said that relatively few Ukrainians have so far sought a haven in countries to the west of their homeland.

A total of 700 have so far applied for asylum in Poland, Belarus, the Czech Republic and Romania, she said.